#1 Marcus Rashford
Rashford will actually turn 20 on 31st October, but as of now, there's no doubt that he's the best teenager in the division, and arguably one of the best wingers in any age group.
He broke into the first team when Anthony Martial was injured in the warm up to the match against Danish side FC Midtjylland in the Europa League Round of 32. He scored twice in that match in an emphatic 5-1 win, helping the Red Devils overturn a 2-1 deficit from the first leg.
He scored another brace that weekend in a 3-2 win over Arsenal at Old Trafford. United fans were justifiably excited with the latest youngster to have graduated from the famed academy, but what they didn't know then was the vast set of qualities he possessed.
His goals against Midtjylland and Arsenal were typical poacher's finishes, but when Louis van Gaal began utilising him as a wide man (following Martial's return from injury), he began bamboozling the crowd with his extraordinary pace, dribbling and a direct attacking approach.
In his second season at the club, Mourinho continued to use him as a winger, choosing to start him most of the time ahead of Martial. He was nominated for the Golden Boy award, but finished a runner-up to Bayern Munich's Renato Sanches. He made the most number of appearances that season (53) of any United player.
He's already won four trophies at the club, and made 50 appearances, scoring 12 goals. This season, Martial's excellent form has led to Mourinho rotating the duo on the left wing. To his credit, Rashford has managed to keep the pressure on Martial and has featured in every match so far this season, scoring 5 goals and assisting 4 times.
He also has 11 caps for the English national team, and played a match-winning performance in their recent 2-1 win over Slovakia, with one goal and one assist. That performance has almost certainly propelled him up the pecking order, ahead of Sterling and Oxlade-Chamberlain.
While all the players on this list are stars to look out for in the future, Rashford is already a superstar in his own right. He is probably one of the most important players for United right now and will continue being a central figure for both club and country for the next 10 years.